In many applications, such as in lithium ion battery management integrated circuits, for example, high precision voltage measurements are required which necessitate extremely small absolute errors (e.g., <1.5 mV).
These voltage measurements can be carried out using sigma delta analog digital converters (ADCs). Sigma delta ADCs output a bit stream which has a mean value corresponding to the mean value of the input signal, i.e., the “pulse-density,” which is the number of “1” within a predefined total number of bits corresponds to the voltage value measured by the sigma delta ADC.
The output range of a sigma delta ADC (native ADC range) is defined by one or two reference voltages that are, however, not fixed, but may vary with temperature or other physical variables. Therefore, when measuring voltages by means of a sigma delta ADC, the range of the voltages to be measured (corrected result range) has to be smaller than the smallest (“worst case”) native ADC range.
For a transformation of the native range to the corrected result range, the output values are scaled and, if necessary, offset corrected. Due to varying (e.g., temperature dependent) reference voltages, it is desirable that the transformation is adaptively adjustable such that the transformation can be continuously adapted to varying reference voltages. Otherwise, the e.g., temperature stability requirements for the reference(s) would be very high or even not feasible dependent on the required measurement accuracy.
Conventional approaches for carrying out the transformation of the native range to the corrected result range use floating point calculations in a microcontroller to scale the output of a sigma delta ADC. Such a solution is very intricate on chip level and requires a semiconductor technology having high integration density of circuits. Further, when transferring the calculations required for scaling the sigma delta ADC output to a microcontroller, continuous adjustment of the scaling of the sigma delta ADC output to varying reference voltages (due to e.g., temperature changes) will be difficult.
Therefore, there e.g., exists a need for a method and/or system for scaling of sigma delta ADC outputs and/or compensating changes of reference voltages of sigma delta ADCs which require less complex circuitry and lower integration density of circuits.